FIG 2 - uploaded by Rahul Mitra
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(a) X-ray diffraction pattern and (b) electron diffraction pattern from plan-view TEM specimen of as-deposited Al–Ti multilayered film. {111}Al diffraction ring, which coincides with the {0002}Ti, is marked as “1” is shown with an arrow. The {200} Al ring is marked as “2”.
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![FIG. 6. Typical electron diffraction pattern close to [011] Al zone...](profile/Rahul-Mitra-3/publication/231976529/figure/fig5/AS:300377917411329@1448627084026/Typical-electron-diffraction-pattern-close-to-011-Al-zone-axis-from-region-containing_Q320.jpg)
Al–Ti multilayered films (12 at.% Ti) with bilayer period of 16 nm were deposited by magnetron sputtering. The films were annealed in vacuum at 350 or 400 °C between 2 and 24 h. During annealing, a diffusion-controlled chemical reaction between Al and Ti layers led to Al3Ti precipitation. Differential thermal analysis studies showed an exothermic r...
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Citations
... The interfaces with sufficient width due to the formation of reaction zone or segregation of impurity elements in the composites are examined using SEM or EPMA, whereas the elemental composition is assessed both qualitatively and quantitatively by EDXS or WDXS [55][56][57]. On the other hand, the structure of interfaces between matrix and precipitates or reinforcement or between layers in a multilayered nanocomposite coating is examined at different length scales (micrometre to Angstroms) using a combination of conventional and high resolution TEM [58,59]. Using bright-field and dark-field TEM along with SAED analysis as well as high resolution TEM, it has been possible to analyse the orientation relationships between matrix and precipitates [58], as well as examine the presence of coherency or semi-coherency with misfit dislocations at various interphase interfaces [59]. ...
... On the other hand, the structure of interfaces between matrix and precipitates or reinforcement or between layers in a multilayered nanocomposite coating is examined at different length scales (micrometre to Angstroms) using a combination of conventional and high resolution TEM [58,59]. Using bright-field and dark-field TEM along with SAED analysis as well as high resolution TEM, it has been possible to analyse the orientation relationships between matrix and precipitates [58], as well as examine the presence of coherency or semi-coherency with misfit dislocations at various interphase interfaces [59]. Similarly, the presence of nano-scale glassy region often present at the grain boundaries of Si-based ceramics (SiC or Si 3 N 4 ) as well as the matrix-reinforcement (MoSi 2 -SiC) interfaces have been imaged by the combination of conventional and high resolution TEM [10,[58][59][60]. ...
... Using bright-field and dark-field TEM along with SAED analysis as well as high resolution TEM, it has been possible to analyse the orientation relationships between matrix and precipitates [58], as well as examine the presence of coherency or semi-coherency with misfit dislocations at various interphase interfaces [59]. Similarly, the presence of nano-scale glassy region often present at the grain boundaries of Si-based ceramics (SiC or Si 3 N 4 ) as well as the matrix-reinforcement (MoSi 2 -SiC) interfaces have been imaged by the combination of conventional and high resolution TEM [10,[58][59][60]. The amorphous structure of such interfacial layers formed from the segregation of oxide impurities interfacial glassy phase (7-10 nm wide) with typical SAED pattern as an inset showing a diffuse halo (arrowed), and b atomically sharp interface with mono-atomic steps (arrowed) [10]. ...
The development of materials for high performance engineering applications requires unique techniques for microstructural characterization and evaluation of mechanical behaviour at different length-scales. The characterisation of microstructure has been boosted by advanced techniques of high resolution optical, scanning and transmission electron microscopy, as well as orientation imaging, being aptly supported by rapid progress in sample-preparation techniques. Additionally, determination of chemical composition of bulk samples, and interphase interfaces as well as surfaces with depth profiling have become possible along with imaging of microstructure. While X-ray micro-computed tomography has revealed the distribution of porosity or various phases (micrometre scale) within the bulk of samples, atom-probe tomography has made it possible to examine segregation of elements at nano-scale. Furthermore, with advancement of X-ray and electron diffraction techniques, it has been possible to obtain crystal structures and symmetries, as well as to measure lattice constants and residual stress. The evaluation of mechanical behaviour of both conventional and advanced materials, including elastic modulus, hardness, tensile, compressive and flexural properties, creep, fatigue and fracture has progressed with development of standards for test procedures facilitating generation of precise and reproducible test results. Availability of standard testing protocols has also paved the way for design and certification of various types of materials for specific engineering applications. Further, advanced characterisation of microstructure and mechanical properties at different length scales has promoted greater scientific insight into structure-property relationships as well as micro-mechanisms of deformation and fracture of various classes of materials, including metals and alloys, intermetallics, ceramics, polymers and semiconductors, thin films and coatings.
... From the Fig. 6a, it was clear that the stress annealing can effectively improve the forming height at the imprinting temperature range of 25-300°C. This is because the stress annealing accelerated the release of residual stress in the formed parts, and improved the forming limit and plasticity of aluminium foil, while the flow stress, hardness, and strength of aluminium foil decreased in varying degrees (Du et al. 2004;Mitra et al. 2001). This greatly eliminated the influence of the first impression on the subsequent deformation of the formed part, which resulted in the forming was easier at the second impression. ...
The rapid development of mechanical systems’ miniaturization has expanded the demand for higher precision and performance micro formed parts. For improving the forming height and quality of formed parts, and studying the influences of the stress annealing and imprinting times on the forming as well as surface roughness (Sa) of the formed parts, this paper proposed a composite process of imprinting times and stress annealing on warm laser shock imprinting (WLSI) to realize the precision forming of the aluminium foil. In this research, the WLSI experiments were carried out with the imprinting temperature, imprinting times, and stress annealing treatment as variables. Subsequently, the forming height, surface roughness, and surface oxidation of the formed parts were measured, the loading–displacement curve were monitored, the transient deformation process induced by WLSI was divided four stages (deformation stage, rebound stage, vibration stage, and stable stage), and the residual stress distribution of the formed parts were simulated and analyzed by ABAQUS. Finally, the influences of the above three factors on the formed parts were discussed and explicated, and these results showed that the imprinting times and stress annealing can improve effectively the forming effect of WLSI.
... The Ni-based nanocomposite thin films containing ceramic dispersoids have received considerable attention as protective coatings, because of their impressive mechanical properties and corrosion resistance. It has been also demonstrated that such nanocomposite thin films can be processed by both electrodeposition [6,7] and physical vapor deposition methods [8]. Although electrodeposition is an inexpensive process, yet there is a strong possibility of contamination of the films by electrolytic solutions and other chemical reagents. ...
... Based on in-situ tensile straining studies on transmission electron microscope (TEM), it has been inferred that dislocation-based deformation mechanism is operative in grains with 10-20 nm size [16,17]. The presence of intermetallic or ceramic nanoparticles as reinforcement in thin films with nanocrystalline metallic matrix helps in stabilizing the microstructure by restricting matrix grain growth during processing or exposure at high temperatures [18]. The nanocomposite thin films with metallic matrix and ceramic reinforcements have been processed primarily by electrodeposition route [19][20][21][22][23]. ...
Nanocomposite thin films with TiN dispersed in Ni matrix were deposited in an environment having Ar:N2 = 1:2 on silicon (100) substrate with bias of − 60 V at 300 °C, 500 °C or 700 °C by co-sputtering of Ti and Ni targets used as RF and DC sources, respectively. The structure and properties of these films were compared with those deposited at ambient temperature and then annealed for 1 h in vacuum at above-mentioned temperatures. Whereas 〈111〉 is the preferred orientation of Ni, transition from 〈100〉 to 〈111〉 is observed for TiN at temperatures ≥ 500 °C, as confirmed by XRD analyses. The average grain sizes of Ni and TiN have been found to be in the ranges of 11–25 nm and 6–13 nm, respectively, using both XRD and TEM studies. Transition from compressive to tensile residual stress is observed with increase in substrate temperature for deposition or annealing. Hardness, elastic moduli and scratch-resistance of the films evaluated using a nanoindentor are found to possess the most optimum values on their growth at substrate temperature of 300 °C.
... It can be seen that the hardness of W-Ni-N coatings increases at first with the increasing of Ni 3 N phase content and decreasing of W 2 N phase content and reached the maximum value of 38 GPa for coating with phase composition of 0.85 W 2 N + 0.01Ni + 0.14Ni 3 N, and then followed a decreasing trend with W 2 N phase content decreasing and Ni phase concentration increasing. Based on phase composition and TEM analysis it could be concluded that the hardness enhancement is mainly due to the formation of nanocomposite structure with the most appropriate phase composition whereas the decreasing trend of hardness could be ascribed to an increasing contribution of soft Ni phase with hardness below 10 GPa [33] and decreasing of hard W 2 N phase content in the coating. ...
The bonding interface plays an important role in the mechanical properties of laminated metal composites (LMCs). Compared with a straight interface, larger bonding area is achieved by a wavy interface, which provides higher debonding resistance for a given bonding strength. Herein, Al/Ti/Al LMCs with straight and wavy bonding interfaces are fabricated using Ti strips with initial straight and wavy profiles. The mechanical properties are investigated with in‐plane uniaxial tension tests. Microstructures in the region of the interface before and after tension are characterized by scanning electron microscopy and electron backscatter diffraction. Finite element simulations of the rolling‐bonding process and tension are conducted to investigate the effect of the wavy profile on the fabrication and mechanical properties of Al/Ti/Al LMCs. Compared with an initial straight profile, Al and wavy Ti strips are successfully bonded at a lower rolling reduction because of the larger local strain and higher local contact stress. Wavy interfaces between the Al and Ti layers are formed. Similar strength and ductility are obtained for Al/Ti/Al LMCs with straight and wavy interfaces when a proper rolling reduction and annealing are applied.
Structural transformations proceeding in heating of thick multilayer Al/ Ti foils, produced by electron beam layer-by-layer deposition of components from the vapor phase, have been studied using methods of differential thermal analysis, X-ray diffraction methods, and scanning electron microscopy. By means of temperature increase from 350 to 650 °C successive formation of intermetallic compounds of Al--Ti system, enriched with titanium, occurs in the foil. At all stages of transformation (up to 650 °C) structure of the foil is heterophase one.
The effect of substrate bias variation on structure and properties of the Ni–TiN nanocomposite thin films
deposited on Si (100) substrates by magnetron sputtering has been investigated. Deposition has been carried out by reactive co-sputtering of high purity Ti and Ni targets as RF and DC sources, respectively in an atmosphere with Ar:N2 = 1:2. The microstructures of the as-deposited films have been examined using grazing incidence X-ray diffraction and transmission electron microscopy. It has been observed that with an increase in negative substrate bias from 0 to −80 V, the TiN volume fraction increases from 36 to 50%, whereas the average grain sizes of both Ni (≈10–17 nm) and TiN (≈6–9 nm) decrease. Moreover, the biaxial compressive residual stress as
estimated by sin2ψ technique scales with negative substrate bias. The surface roughness determined using atomic force microscopy appears to be the least in the nanocomposite film depositedwith substrate bias of−60 V. Furthermore, X-ray photoelectron spectroscopy studies have confirmed the formation of oxygen-free stoichiometric TiN in this film. Hardness (≈12.6–16.9 GPa), elastic modulus (≈208–233 GPa) and scratch-resistance determined by nanoindenter, as well as electrical resistivity (≈26–47 μΩ·cm) measured using dc four-probe method, are found to scale with TiN content. An increase in hardness and electrical resistivity with an increase in negative substrate bias is also attributed to a decrease in Ni grain size and an increase in point defect density.
Thin films of Ni-TiN nanocomposites have been deposited on Si (100) substrate at Ar:N2=1:1, 1:2 or 1:3 at ambient temperature by reactive co-sputtering of Ti and Ni targets used as RF and DC sources, respectively. X-ray diffraction (XRD) studies have shown <111> and <200> as preferred orientations for Ni and TiN, respectively. X-ray photoelectron spectroscopic examination of the films has shown Ti/N to be 1 for Ar:N2 = 1:2, and < or >1 for Ar:N2 = 1:1 or 1:3, respectively. Scanning and transmission electron microscopic studies have shown that with increase in Ar:N2 from 1:1 to 1:3, both porosity content and grain sizes are reduced, while the TiN volume fraction obtained by Rietveld analysis of XRD peaks is increased from 22 to 44%. The magnitude of compressive residual stress in both Ni and TiN phases is found to increase with decrease in Ar:N2 ratio. Nanoindentation studies have shown that hardness and elastic moduli of films increase with TiN content closely following the rule of mixtures, whereas the scratch resistance scales with hardness. Furthermore, resistivity measured by Van der Pauw four-point probe method appears to be proportional to the TiN volume fraction.
